U.S. specialty chemicals company Rockwood Holdings has attracted bids from private equity groups for its industrial ceramics unit CeramTec, people familiar with the deal said.

Permira, Cinven, BC Partners, TPG Capital and Bain Capital have handed in second-round bids by a Friday, April 26, deadline, people familiar with the investors said.

Private equity firms like France's Wendel and Chicago-based GTCR have also attended management presentations over the last weeks, though it was not immediately clear whether they were also among the bidders, one source familiar with the transaction said.

Bids came in a range of roughly €1.2 billion to 1.5 billion ($1.6-$2 billion), two sources said.

The offers are being backed with debt packages of around €900 million, or 6.5 to 6.75 times CeramTec's approximate €135 million in EBITDA (earnings before interest, taxes, depreciation and amortization), bankers said.

Rockwood and Lazard - which is managing the sale of the Germany-based unit - declined to comment. The private equity firms also declined to comment except for Wendel and GTCR, which were not immediately available for comment.

The deal is one of a growing number of asset sales in Germany as improved euro zone sentiment and a build-up of liquidity following a dearth of mergers and acquisitions last year has increased the availability of bank financing and helped create the most attractive prices in years.

Rockwood has decided to sell CeramTec as it seeks to focus on lithium, for which demand is increasing due to the advent of lithium batteries in cars and the rising popularity of smartphones and tablets, which need longer-running batteries.

CeramTec, which was founded in 1903, produces ceramics that go into thousands of products from filters for water treatment to electronic components in factory robots. It had sales of $548 million in the 12 months to September.